Fluoroelastomer coating compositions are well known. They typically comprise copolymers of vinylidene fluoride and hexafluoropropylene or terpolymers of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene.
Fluoroelastomers are well known for their heat, weather, solvent and chemical resistance. Furthermore, cured fluoroelastomer films typically exhibit good mechanical properties and adhere to a variety of surfaces. As a result of these properties, fluoroelastomer coating compositions are applied to protect a variety of surfaces including metals, plastics, rubbers, concrete, glass and the like.
Heretofore in the art, fluoroelastomer coating compositions have been applied by using organic solvent systems. Typical solvent systems employed ketones or ethers. Such solvents, however, are hazardous to use inasmuch as they are flammable, toxic, and volatile. Moreover, growing environmental concern over the use of such volatile organic compounds restricts the use of such compounds in various areas of the country. Finally, the pot life of the fluoroelastomer coating compositions employing such solvents is generally only a few hours. Pot life, as it will be used herein, refers to the time required for the fluoroelastomer coating composition to begin gelation.
Water-borne fluoroelastomer coating compositions are also known. For example, DuPont de Nemours Company, of Wilmington, Delaware teaches aqueous dispersions of their fluoroelastomer, VITON.RTM., with a polyamine curing agent. The pot life of such dispersions, however, is relatively short, generally only 2 to 5 days. Ausimont U.S.A. also teaches aqueous dispersions employing their fluoroelastomer, TECNOFLON.RTM., with aliphatic amines as curing agents. As with the dispersions taught by DuPont, those employing aliphatic amines also have a relatively short pot life, on the order of only 3 to 5 days.
U.S. Pat. No. 4,399,553 also teaches a water based fluoroelastomer coating composition containing partially or completely hydrolyzed aminosilane compounds, with or without additional amine compounds, as curing agents. These aqueous dispersions are taught to have a pot life of up to one month at 25.degree. C.
Thus, although water based fluoroelastomer coating compositions are known, a need still exists for a water based fluoroelastomer coating composition having improved pot life, excellent stability, and which produces cured films with excellent adhesion to a wide variety of substrates.